| Abstract: | Summary. Blood and muscle metabolite levels were measured in seven healthy young adult male subjects in a fed state and again following a 24-hour fast. Skeletal muscle samples were obtained under local anaesthesia from m. vastus lateralis using a needle biopsy technique. The blood glucose concentration fell during fasting; the blood lactate concentration remained unchanged. Plasma free fatty acid concentrations rose, as did 3-hydroxybutyrate and acetoacetate levels. There was no change in the amount of carbohydrate stored as glycogen in the muscle in response to fasting. The muscle content of phos-phagens (adenosine triphosphate and phosphocreatine), glycolytic intermediates (glucose-6-phosphate, fructose-6-phosphate, fructose-1, 6-diphosphate, triose phosphates and lactate) and citrate was also not affected by fasting. There was a significant increase in the muscle content of 3-hydroxybutyrate. These results give no indication as to the mechanism by which a decreased rate of carbohydrate degradation might occur in muscle in the fasted state. It is clear, however, that an intracellular accumulation of citrate and a consequent inhibition of glycolysis at the level of phosphofructokinase does not take place in fasting human skeletal muscle. |
